The present invention relates to a biological parameter displaying apparatus which automatically plots data related to two biological parameters (particularly cardiovascular parameters such as the blood pressure and the cardiac output) of different kinds that are acquired from a living body at the same time or in the same time zone, in XY coordinates, and which can display the data in the form of a trend display so as to clarify the plotted time sequence.
In order to know the trend of the circulatory dynamics, there is an apparatus which performs a trend display such as shown in FIG. 8. A trend display is a display in which the ordinate shows the values of biological parameters, and the abscissa shows the time. In the trend display of FIG. 8, temporal changes of biological parameters in the medium and long term can be easily known, thereby providing beneficial information to the a medical person.
As a graph showing a relationship between two different biological parameters, there are a cardiac function curve and the Forrester classification in which data related to two biological parameters acquired from a living body are displayed in XY coordinates.
In a cardiac function curve, the cardiac index CI is set as the Y-axis (ordinate), the pulmonary artery wedge pressure PCWP is set as the X-axis (abscissa), and data are plotted in XY coordinates as shown in FIG. 7. From the drawn curve, a medical person can easily know the circulatory dynamics such as whether the cardiac function is normal, decreased, or enhanced.
In the Forrester classification, similarly as shown in FIG. 7, for example, XY coordinates in which a cardiac function curve is displayed is divided into four events, and the events are classified as “I Normal”, “II Mild”, “III Low cardiac output”, and “IV Low cardiac output+pulmonary congestion”, respectively. Depending on the position where the data (indicated by the circles) of the patient are plotted, a medical person can easily know the circulatory dynamics such as a pathological condition due to cardiogenic shock.
In the trend display which is shown in FIG. 8, the abscissa is the time axis, and hence only temporal changes of parameters are known, so that the circulatory dynamics based on the linking of two different biological parameters cannot be known.
A graph such as shown in FIG. 7 is usually produced by first independently measuring two different biological parameters, and then plotting the data to form the graph. It cannot be always said that such a graph is produced by plotting data of two different biological parameters having appropriate temporal relationships.
The reason of this is as follows. In the case where the cardiac index CI and pulmonary artery wedge pressure PCWP shown in FIG. 7 are measured, an invasive technique in which a pulmonary artery catheter having a balloon at the tip end is inserted into the heart of the patient is employed. Moreover, the cardiac index CI is a value which is acquired by performing division on the cardiac output CO. In order to acquire the cardiac output CO, it is necessary to perform the thermodilution method or dye dilution method in which a medical person injects a predetermined solution into the patient in each measurement. Moreover, the pulmonary artery wedge pressure PCWP is a blood pressure in the case where the balloon at the tip end of the pulmonary artery catheter is inflated. In order to acquire the pulmonary artery wedge pressure PCWP, therefore, a medical person must inflate the balloon in each measurement. Therefore, data of the ordinate and the abscissa which are acquired by operations conducted by a medical person cannot be continuously measured.
Recently, an apparatus which can continuously calculate the cardiac output CO has been developed. In order to plot data in coordinates with temporal simultaneousness, however, a plurality of medical persons must respectively perform measurements, or a single medical person must simultaneously perform the measurements. Therefore, it cannot be said that the workability is high.
In the case where a graph such as shown in FIG. 7 is applied as a trend display of, for example, the circulatory dynamics of a living body, particularly, plotting must be performed while further considering the temporal simultaneousness of two different biological parameters. Even if simultaneous measurements are performed and data can be plotted in coordinates, the display is shown in the form indicating the time sequence. Although a technique in which the time is directly written as in FIG. 7 may be considered, there is a problem in display such as that, when the number of data to be plotted is increased, the data are hardly readable.
U.S. Pat. No. 7,542,795 and Japanese Patent No. 3,656,642 disclose art in which two different biological parameters are displayed in coordinates.
In U.S. Pat. No. 7,542,795, results of measurements by one electrocardiogram sensor are plotted in the ordinate and the abscissa. In Japanese Patent No. 3,656,642, the maximal and minimal blood pressures which are results of measurements by one blood pressure sensor are plotted in the ordinate and the abscissa. In the above art, it cannot be said that the measurements results are two different parameters, and the circulatory dynamics based on the linking of two different biological parameters cannot be known.